1. Technical Field
The present invention relates to a temperature compensation circuit (a temperature compensation voltage generating circuit) and the like.
2. Related Art
An analog reference voltage (a direct current bias voltage) on a signal path (or a circuit) varies depending on an ambient temperature. If the variation of the analog reference voltage is compensated with high accuracy, sensing accuracy of a sensing circuit that detects physical quantity, for example, can be improved.
JP-A-2001-267848, for example, discloses a temperature compensation circuit. JP-A-2001-267848 discloses an oscillator (a temperature compensation type oscillator) provided with the temperature compensation circuit (a temperature compensation voltage generating circuit).
Characteristics of elements formed in an integrated circuit device (IC) vary in accordance with variations of element sizes, variations of conditions of a manufacturing process, or an environmental temperature (an ambient temperature). Further, since a noise is superimposed along the signal path, an adverse effect of the noise can not be ignored. Thus, it is difficult to generate a voltage that is temperature-compensated with substantially high accuracy by the temperature compensation circuit.
Further, in a case of temperature compensation of an analog reference voltage (a direct current bias voltage) AGND (analog ground) on the signal path (or a circuit), a temperature compensation voltage VTS that is highly accurate is generated so as to be added to the analog reference voltage AGND. That is, when a temperature-compensated reference voltage (also referred to as a temperature-compensated voltage) is denoted as Vtemp, Vtemp=AGND+VTS is satisfied. Namely, the temperature compensation circuit is required to generate the temperature compensation voltage VTS that is highly accurate for the analog reference voltage AGND.
In related art, a circuit itself has a temperature characteristic, and characteristics of the circuit vary in accordance with variations of element sizes or variations of a manufacturing process. Further, since a noise is superimposed along the signal path, an adverse effect of the noise can not be ignored. Therefore, it is difficult to generate the temperature compensation voltage VTS that is highly accurate. Further, in order to obtain the temperature-compensated voltage Vtemp, the temperature compensation voltage VTS that is generated needs to be superposed on the analog reference voltage AGND. There is no circuit that performs the superimposition of the voltages (addition of the voltages) with high accuracy in an efficient manner, in related art. Thus, the temperature-compensated voltage (Vtemp), described above, can not be generated with substantially high accuracy in an efficient manner.
The temperature characteristic of the circuit is variable. Therefore, in circuit designing, it is desired that the temperature characteristic of the temperature-compensated voltage (Vtemp) can be flexibly changed in a manner corresponding to the temperature characteristic of the circuit. Related art does not have such flexible temperature compensation circuit. Thus, it is difficult to realize a temperature compensation circuit that is capable of compensating variable temperature characteristics of the circuit and has high adaptability.